Gene responsible for toxic metal accumulation in durum wheat identified

Researchers complete genome assembly of durum wheat, identify gene responsible for cadmium accumulation.

Katie Willis - 8 April 2019

University of Alberta biologists identify gene responsible for cadmium accumulation in durum wheat, according to a new study published in Nature Genetics. For humans, consuming cadmium, a toxic metal that accumulates in grain crops, poses serious health risks, including cancer and kidney disease.

"The mechanism responsible for high cadmium accumulation in Canadian varieties of durum wheat has, until now, remained elusive," said Neil Harris, researcher in the Department of Biological Sciences and co-author on the study. Canada is the world's leading exporter of durum wheat, providing approximately 50 per cent of global durum exports.

Food safety

Cadmium, which naturally occurs in soil, is absorbed into plants through the roots. The gene-named TdHMA3-B1-produces a metal-transporting protein that stores cadmium in roots preventing its transport up to the shoots and grain. "Our work identified a mutation in TdHMA3-B1 that disrupts its function. Durum wheat varieties with the non-functional TdHMA3-B1 are unable to restrict cadmium transport to the grain," said Harris.

"A genetic marker for the mutation is now being used to screen all Canadian durum breeding lines, enabling rapid development of low-cadmium durum wheats. As a result, all durum wheat varieties now released in Canada accumulate two to three-fold less cadmium in their grain, thereby increasing the quality and safety of pasta and couscous, the primary products derived from Canadian durum wheat."

The identification of TdHMA3-B1 is one of many practical applications of how understanding the durum wheat genome can improve food security and safety. Others include improved yield, insect and disease resistance, and resilience to environmental stresses arising from climate change such as heat and drought.

The study was conducted in collaboration with Gregory Taylor, professor, and Kevin Liang, undergraduate student in the department. The paper, "Durum wheat genome highlights past domestication signatures and future improvement targets," is published in Nature Genetics (doi: 10.1038/s41588-019-0381-3).